I just got a dp3 too and compared to my k5 with fa 50 f1.7 or da* 50-135 f2.8 its miles ahead for IQ but only in the situations it shines in.
This shot was with the k5 and da* 50-135 at the top and the sigma dp3m at the bottom, both camera's focused onto the light stand and default sharping.
Here's another 100% crop from the dp3m
The detail this lens/camera combo resolves is amazing and I like the color rendition too.
This one is the k5 with fa 50mm f1.7 vs the dp3m
This was the first test I had done and It really made me think my k5 was broke or miss focused (I focused using live view at 8x?) so I re took the shot with the 50mm prime and then with my da* 16-50 and the results were the same.
Both camera's set to the same settings in all shots with the k5 needing a +0.6ev boost to match the sigma.